The neuromodulatory neurotransmitter dopamine (DA) plays a complex, but central role in the learning and performance of stimulus-response (S-R) behaviors. Studies have implicated DA's role in reward-driven learning and ...

Nicotine and other drugs of abuse can act as zeitgebers and entrain persisting circadian activity episodes when administered on a 24-hour schedule. There are two types of drug-induced circadian activity episodes: a ...